Electronic amplifying coupler and system therefor



July 18,1939.

T. W. VARLEY ELECTRONIC AMPLIFYING COUPLER AND SYSTEM THEREFOR 3Sheet-Sheet 1 Filed July 1, 1937 IN VENTOR.

THOMAS W I/AEL/SK N UN ATTORNEYS.

July 18, 1939. w VARLEY 2,166,775

ELECTRONIC AMPLIFYING COUPLER AND SYSTEM THEREFOR Filed July 1, 1957 3Sheets-Sheet 2 THOMAS /t. K JELEY INVENT OR.

BY Wa y/ 4 ATTORNEYS.

July 18, 1939. T. w. VARLEY ELECTRONIC AMPLIFYING COUPLER AND SYSTEMTHEREFOR Filed July 1, 1937 5 ShGtS-Sheet 3 INVENTOR.

ATTORNEYS.

,THOMAS M VAEL-Ek rmdnl iaiaso by mesne 1 Stamford, Conn.

tatollarry Application July 1,1931, Serial N 151.311

20 cum.- (c1. its-1) J This invention relates to improvements inelectronic amplifying relays or couplers and systems therefor, and ithas special reference to such devices as are employed in various systemsof two-way communication, such as signalling, telephone or other typesof two-way communication, whreit is desirable-unnecessary to compensatefor energy losses by amplifying the electrical waves produced in tosignals or sounds.

The invention is applicable to many classes of service. One example iswhere it is desired to interconnect two separate and independenttelephone'or other systems of two-way communication, such as a publictelephone system and a private interoflice telephone system of the same.or of diflerent types, so that any pai'ty on the v 7 interior telephonesystem may communicate with a party on the public telephone system. Withmy invention, such an interconnection can beestablished through theintermediary of my electronic amplifying coupler which is interposedbetween the two systems, either by means of acoustical couplings or bymeans of direct elect'rical connections.

It is also useful in business offices, where one or more persons,perhaps at a conference table. desire to discuss matters with anotherabsent party over the telephone. Under such circumtances, the incomingmessages are received over a speaker in the room, while a sensitivemicrophone enables any of the persons present to talk over the telephonewith the absent party, without leaving his seat.

In telephone service, repeatingrelays of various types are frequentlyemployed in long distance communication; and this'field of service isanother example of one to which my invention pertains.

My invention'is applicable to other fields of use for handling two-waycommunications of various kinds, but the examples above referred to,

together with others which will follow will indicate to some extent itsbroad range of usefulness.

It is one of the objects of my invention to provide a two-waycommunication system of the general character indicated in which theelectronic amplifying couplerequipment employed is not only simple andinexpensive to construct and maintain, but which functions effectivelyto meet the service conditions, while at the same time preventing mutualinterference, and feed back disturbances and, furthermore, is soarranged that breaking in by either party to the conversation may takeplace at any time in the same manner as in ordinary telephoneconversations.

Still another object of my invention is to provide asingle electronicamplifying coupler mwhich the electrical waves of a two-waycommunication, are alternately interrupted at a high periodicity aboveaudibility before being trans-. 5

mitted to theelectronic amplifier, while the amplified and interruptedelectrical waves emanating from the amplifier imit are passed onalternately at the same high periodicity above audibility to therespective outgoing two-way system.

Another object of my invention is to provide such an electronicamplifying coupler in which suitable means, preferably but notnecessarily employing oscillations of .a high frequency above audibilityfrom an extraneous source in connection with rectifying means, areutilized to interamplifying means, so that the amplification is eflectedupon a continuous series of unidirectional pulsations of a suficientlyhigh frequency that the intermittent or non-continuous character of themodulations of electrical waves being transmitted and amplified, is notdetectable'to the human ear when received as sound waves and thereforeis heard or experienced as though it were actually unbroken a dcontinuous.

Another object of my vention is to provide a unitary signal or telephonesystem, which either may include two separate and electricallyindependent signal or telephone systems, such as, for instance, anordinary public telephone system and private interior or inter-omcetelephone system,"

or two successive sections or parts of a single telephone system such asis used for long distance communication, and in which thecomoperating'in conjunction with a high frequency oscillator, in' suchmanner that the single electronic amplifying device serves both circuitsof the system in common but at alternate time periods, wherebycontrollable amplification of the 4 electrical waves of a two-waycommunication is accomplished with complete absence of" mutual "systemsof, communication or parts of a single two-way system and which embodieselectronic amplifying coupling means of the above indicated type, whichisjarranged and adapted to sepa- M circuits of the ,10

rately and alternately amplify or intensify the electrical waves beingtransmitted in both directions, while positively preventing anyinterference between the two-way communication and entirely eliminatingthe possibility of feed back disturbances.

A further object of my invention is to provide an electronic amplifyingcoupler adapted for signal, telephone or other service which embodies asingle amplifier unit, which is permanently connected into therespective two-way operating circuits of the system or systems, butwhich is so constructed, arranged and controlled as to alternatelytransmit and amplify the electrical waves of a two-way communication,in, such manner that a rapid succession of intermittent, alternate,unidirectional impulses are obtained, first from communication in onedirection and then from the other, and at a sufliciently high fre-vquency above audibility as to obviate any detectable audible efiect tothe listener upon the si nals or sounds being received, while at thesame time, by reason of the alternate 180 time phase displacement of thealternate unidirectional impulses through the amplifler unit,positivelyand definitely preventing any mutual interference or a feedback disturbances.

7 Another object of my invention is to provide an acoustically coupledsignal or telephone system in which two electrically independent andseparate systems or two successive sections or portions of a singlesystem, may be coupled together acoustically for two way communication,by means of a single electronic amplifying coupler which serves bothcircuits of the two-way system in common but at rapidly alternating timeperiods, without interfering with the usual circuit connections oroperation of the thus inter-connected systems or sections of a singlesystem.

In accordance with one aspect of the invention. and quite apart from andindependent of its application to any particular field of service, Icontemplate the use of a single electronic amplifying coupler which ispermanently connected with both circuits of a two-way communicationsystem. The amplifying unit per se may be of any well-known type andembody one or more stages of amplification and, if desired, the usualpush-pull power tubes. This sin le amplifying unit, however, which, ofcourse, is uni-directional, functions for both circuits at all times, sofar as can be detected by the human car, so that either party to theconversation can breabat any moment.

Thus, with but a single ampllfr na unit, apparent concurrentconversations between the parties can take place, and yet without mutualelectrical interference or feedback.

This is accomplished by the manner and the means by which the amplifyingunit is controlled and permitted tofunction. To effect the desiredcontrol, Ipreferably utilize a high' frequency oscillator in conjunctionwith suitable rectifying devices so as to alternately interrupt theincomin: electrical waves from each direction to the amplifier at a highrate or periodicity above audibility. By similar means I alternatelyinterrupt the respective outgoing electrical waves from the amplifier inthe same manner and, moreover, I dosoinexactstepwiththeinterrupflcmoftheincoming waves.

In other words," the incoming and outgoing waves passing through thesystem in one direction are simultaneously interrupted in precise stepor time relation, whereas the incoming the amplifying unit per se isoperative at all times to pass uni-directional waves through it in asuccession of rapid'intermittent pulsations, still every alternatepulsation constitutes a part of the electrical waves passing through thesystem in one direction, while the intermediate alternate pulsationsconstitute parts of the electrical waves passing through the system inthe opposite direction.

' Yet, the frequency of the respective interruptions is so high withrespect to the normal frequency of the electrical waves beingtransmitted and amplified, that the interruptions are not discerniblewhen received as sound waves by the human ear, and the amplified signalsor sounds heard by the listener appear as continuous and clear.

By reason of the character of control of the amplifying unit per sewhereby it functions alternately on electrical waves passing in oppositedirections through the system, it will be understood that it isactive'to waves passing through the system in one direction during everyalternate pulsation, and at the same time dead to waves in the oppositedirection. Similarly. the

intermediate alternate pulsations are active to the waves passingthrough in the other direction and dead to those of the first direction.'Therefore, there is no possibility of feed back disturbances or mutualinterference, no matter how close together the receiver or speaker maybe placed to the transmitter or microphone at either end of the system,and also entirely independent of .the degree of amplification orintensity.

The oscillator may be of any well-known construction and in general ispreferably designed to deliver oscillations at a frequency aboveaudlbility. Ordinary voice frequencies. range generally from 100 to 1000cycles per second, while music may range from perhaps 60 to 6000 cyclesper second. In my invention, an oscillator having a frequency of 20,000cycles per second will give excellent results, although in someinstances, it may well range from about 5000 to 45,000 cycles or evenhigher. The particular frequency is not critical, so long as it issufficiently higher than that of electrical waves being transmitted andamplified, as to obviate any objectionable interference.

The rectifying devices employed in connection with the oscillator arepreferably of the dry copper oxide type. known in the art as Rectox",web as that described in Patent #1,640,335 granted August 23, 1927, toGrondahl, although my invention is not limited to rectifiers of thisThese and other objects of the invention and features by means of whichthey are accomplished will become more apparent from the followingdescription of the invention in connection with the accompanyingdrawings in which Lia a diagrammatic view-of the circuit the circuitconnections of a modified form of telephone system embodying myinvention;

Fig. 3 is a diagrammatic view of a portion of the circuit connections ofa further modification, and

' Fig. 4 is a diagrammatic view of .a still fur-: ther modification ofmy invention.

Referring now to the drawings, and particularly to Fig. 1 thereof, myinvention is illustrated as interconnecting a plurality of electricallyindependent telephone systems A and B, which are connected' together soas to function as a single system of two-way communication through theinterposition of my amplifying coupler C.

The telephone system A may, for example, comprise an ordinary publictelephone system having a plurality of subscribers stations, only two ofwhich are indicated in the drawings and are represented-for illustrativepurposes by the French telephone sets F1 and F2, the latter oi whichcomprises a receiver R: and a transmitter T2. The telephone system B,which is entirely independent of the telephone system A, typifies anyordinary private interofflce telephone system 'having a plurality ofparty stations, only two of which are indicated and are represented bythe French telephone sets F3 and F4, the latter of which is providedwith a receiver R4 and a transmitter T4. Both of these independenttelephone systems, A and B, are adapted for twoway conversation and areconnected and operated in any of the usual well-known manners.

For purposes of explanation it will be assumed that the French telephoneset F2 of the public telephone system and the French telephone set F4 ofthe interoflice system are located on or near the desk 'or' in theIroomof the, telephone operator in a private business office or factory wherethe desired telephone connections for the public telephone system or forthe interofflce system may be readily effected by the operator.

In order to make provisions for enabling twoway communication betweenany party to the interoftice telephone system and a party to "theoutside or public telephone system, the amplifying coupler C,constituting my invention, is located within convenient reach of -theoperator and is arranged so that it may be readily connected as anintermediary agency between the.

tronic amplifier unit, E of any conventional type and may embody one ormore stages of amplification, together with one or more power tubes,-

which, if desired, may-be arranged in the well:

known push-pull relation, as willbe readily understood without furtherdescription. In the drawings, only the first amplifying tube 2 and Theinput side of the amplifier unit E has its first amplifying tube 2connected to a microphone Msthrough conductor {resistance l0 andconductor II, the other terminal of the microphone being connected toground by conductor l4. The amplifying tube 2 is also connected tomicrophone Mb throughconductor 8, resistance l6 and conductor ll, theother terminal ofthe microphone being connected to ground throughconductor II. The two microphones M. and lb are therefore connected inparallel relation The output side of vthe amplifier unit E has its powertube 4 connected through conductor I2,

condenser 24 and conductor 20 to one terminal of a winding 20 of anauxiliary transformer 30,.

and thence from the other terminal of winding II by conductors II and 32to one terminal of a winding 34 of an auxiliary transformer-3i, and

from the other terminal, of winding 34 thence by conductor 38, condenserand conductor 42,"

In order to make use of the amplifying unit E,

the operator establishes acoustical couplings between the unit and therespective telephone systems A and B, by placing the French telephone F:

. with its receiver R: and transmitter T2 in proximity to and inacoustical relation with the micro phone M..and speaker Sb, and also byplacing the French telephone F4 withits receiver R4 and transmitter T4in proximity to and in acoustical relation with the microphone Ms andspeaker Sn, respectively. associated in this manner, the soundwaves aretransmitted acoustically to and from the amplifying unit E without anyelectrical connection whatever with the telephone systems A and B beingnecessary.

So .far as already described, it will be evident that sincemicrophones'Ms and Mb are both connected to theinput side of theamplifying unit E,

It will be understood that when,

and the speakers S3 and So are connected to the output side thereof, theamplifying unit is arranged to amplify incoming electrical waves ormessages emanating from either one or both of the telephone systems Aand B. This, of course, would be entirelyimpractical by reason ofinherent mutual interference and feed back disturb-.

directions, from one telephone system A to the other telephone system B,or vice versa. This is accomplished by controlling the operation of theelectronic amplifier E so that, while functioning at all times, italternately operates upon electrical waves passing in oppositedirections In other words, it is rendered active upon theelectricalwaves passing in one .direction for a very brief increment oftime during which it is in-v active upon the electrical waves passing inthe opposite direction, and then becomes active for a like timeincrement upon the waves passing in the latter direction while beinginactive upon the graves passing in the first direction, and so on intimed alternation,

Similarly, the output side of the amplifying unit E is correspondinglycontrolled so that when the amplifier E is active upon electricalwavesset .up through microphone Ma, these amplified waves are passed onthrough speaker S9,, while when the amplifier unit E operates uponelectrical waves emanating from microphone Mb, these means of which Ihave secured excellent results.

This apparatus includes an oscillator O, which in most instances shouldbe of a relatively high frequency, as compared with that of theelectrical waves produced by sounds or speech, being transmitted overthe system, the general range of frequency having already been hereinbefore set forth. The oscillator 0 may be of any wellknown type ofconstruction and, therefore, it is not shown and will not be describedin detail, except insofar as is necessary to a clear understanding of myinvention. As shown, the oscillator includes a plurality of windings W1,W2 and W3, although a single winding may well take the place of windingsW2 and W: or, if desired, only a single winding may be used, providedproper taps therefor are employed.

Operating in conjunction with and connected to the oscillator in themanner hereinafter described, I employ a plurality of rectifyingdevices, of which I have found those of the dry The rectifying deviceRXs is connected in shunt to the microphone Ma by means of a conductor54 which is connected to its upper terminal and a conductor 55 whichconnects its lower terminal with ground. The positive terminal'of thedevice is.connected through resistance 58 and conductor 60 to oneterminal of winding W2 of the oscillator 0, while the other terminal ofsaid winding is connected by conductor 62 to the negative termine! ofthe rectifying device. In a similar manner the rectifying device RXb isconnected in shunt to the microphone Mb.

The rectifying device RYb is connected in shunt' to the winding 34 ofauxiliary transformer N,

which is associated with the speaker Sb, through.

a conductor 64 which connects to the upper terminal of the rectifyingdevice, while its lower terminal is connected through a reactance O6 andconductor 68 to the other terminal of the trans former winding 34. Thepositive terminal of the rectifying device is connected by conductor Illthrough resistance 12, conductor H and conductor 18 to one terminal ofthe oscillator windunderstood. I

log W1, while the other terminal of said winding is connected byconductor 11, conductor II, resistance 80 and conductor 82 to thenegative terminal of the rectifying device. In a similar manner, therectifying device RY. is connected in shunt to the transformer coil 28of auxiliary transformer 30 which is associated with the speaker 8-,whileth'e positive and negative terminals of the rectifying device RY.are connected across the oscillator winding W1, as will be readily Sincethe various rectifying devices above referred to are similar inconstruction and operation, except that devices RYi and RY, are ofgreater capacity in view of the fact that they are required to handleamplified electrical waves, it is deemed sufiicient to briefly, outlinethe operation of a single one of these devices, for instance rectifyingdevice RXa, which is connected in shunt to the microphone Ma.

For purposes of illustration, let it be assumed that sound waves aretransmitted acoustically from receiver R2 of the French telephone set F:to microphone Ma, which is connected, as already described, to the inputside of the electronic amplifier E, with the rectifying device RXaconnected in shunt to microphone Ma. Obviously, the electrical waves setup in the microphone Ma will tend to divide between that branch of thecircuit which is connected to the amplifier tube 2, and that branchwhich is connected in shunt to the microphone Ms. through the rectifyingde vice RXs, the microphone Ms being rendered ineffective by reason ofthe high resistance IS in the conductor I8 which is connected thereto.The degree or amount of energy of the electrical waves passing to theamplifier tube 2 will depend upon the degree and the amount of energy ofthese waves which are permitted to pass to ground through the rectifyingdevice RX; in

shunt to the microphone Ma, and this in turn will depend upon thepolarity and amount of voltage generated by the alternating currentoscillator at any particular instant. If the voltage developed in theoscillator winding W2 at any particular instant is positive and alsoequal to or greater than the voltage of'that portion of the electricalwaves passing through the rectifying device at that instant, no currentwill be allowed to flow from the positive terminal of the rectifyingdevice through the ,winding W: and thenceto the negative terminal'jofthe rectifying device. Under such circumstances, no effective shuntcircuit from the microphone Mn to ground is established and the entireenergy of the electrical waves being transmitted from the microphone Mawill pass to the first amplifying tube 2 of the amplifier unit E. p

This condition prevails throughout that portion of the high'frequencypositive oscillation during which the generated voltage is equal to ,orgreater than the voltage of the electrical waves,

' and throughout this interval the amplifier E is operative or active totransmit and amplify the electrical waves passing from the telephonesystem A to the telephone system 3. During this particular timeinterval, however, the rectifying device ax, which is connected in shuntto the microphone Mb, is rendered active to pass current to ground byreason of the fact that the voltage of positive polarity generated bywinding W: is added to that of the electrical waves emansting from -themicrophone Mb. Thus, the microphone Mn is rendered inoperative by reasonof the shunt circuit established through the rec- V tifying deviceRx.Hence, during the time interval in question, the amplifying unit Eis-active as to electrical wavespassing from telephone system A totelephone system B, but is, inactive to electrical waves in the oppositedirection.

electronic amplifier unit I will be operative and active upon electricalwaves passing fromtelephone system B to telephone'system A, while itwill be inactive to electrical waves passing in the opposite direction.

For proper operation, it isnot only necessary to properly control theamplifying action of, the

amplifier unit 1!, but to definitely control the output circuits of theamplifier in order that the amplified waves shallbe transmitted on inthe right direction to the proper telephone systems A- and B. For thispurpose the oscillator winding W1 and the rectifying devices RY and RYare employed, and. operate in a generally similar mannet to that alreadydescribed to control shunt circuits across the windings I8 and II of theauxiliary transformers 30 and 36, respectively,

which are associated respectively with the speakers S. and St.

For instance, at the same instant and throughout the duration of theincrement of time that the oscillator winding W2 opp ses the voltage ofthe rectifying device Rx, the oscillator winding W1 generates avoltage'of positive polarity which 'is added to that of the rectifyingdevice RYb.

Therefore, current or energy passes from the posi- .tive terminal of thedevice RYs through the winding W1, to the negative terminal of thedevice RYs and thence to ground. Thus, a shunt circuit is establishedacross the winding 34 of the transformer 36, which transformer and itsassociated speaker Sb, become inoperative. The

opposite is true with respect to the transformer winding 28 oftransformer 30, and its associated speaker Si -that is, no shunt circuitis established across the transformer winding 28, which thereforeoperates to pass onthe amplified elec- 'trical waves through thetransformer 30 to the speaker Si. According during the same interval oftime when the electronic amplifier E is active upon electrical wavespassing from telephone system A, and inactive on waves in theoppositedirection, the speaker Si is active to pass on the amplifiedwaves to thetelephone system 13,

while the speaker Sb is inactive and thus prevents the electrical wavesfrom being passed on back Iii) to telephone system A.

' From the foregoing description it will be manifest that the amplifierunit E operates alternately on the electrical waves passing through theinterconnected system in opposite directions, while thespeakers S- andSb are alternately rendered effective to pass the amplified electricalwaves on in the proper direction and to the proper tele phone systemA orB, as the case may be. The electrical waves being amplified and passingthrough the interconnected. systems in opposite directions are thusalternately interrupted and amplified at a frequency depending uponthefrequency of oscillator O, which maybe sufficien ly high, if desired,with respect to the frequency of the electrical waves passing throughthe system that the successive. interruptions are above audibility andtherefore have no discernible effect upon the ear of the listener who.hears the sound waves emanating from his receiver, 'exactly as thoughthey were uninterrupted or continuous.

By this method of control of the operation of the amplifier unit E,whereby the microphone Ma and the speaker S. are simultaneouslyoperative,

and the microphone Ma and the speaker Sb are inoperative, and viceversa, in alternation, it is a physical impossibility for mutualinterference and feed back disturbances to result from a two-wayconversation, each part of which is definitely and positively separatedfrom the other by the 180' time phase displacement utilised in thecontrol of the amplifier operation by reason of the high frequencyowillator O, and irrespective of the volume or intensity of the soundemanating from the receiver or speaker at the receiving end of thesystem, or its degree of proximity to the transmitter or microphone atthat end of the system.

- While my invention has been described in con neotion with Fig. 1 as anamplifying coupler for two separate and independent telephone systems,such as a public telephone system and wintersimilar manner'tointerconnect two sections of a single telephone system, as is done inlong distance telephone transmission. Moreover, the interconnection ofsections of asingle system may be effected acoustically as shown anddescribed in connection with Fig. 1 or the interconnecting amplifyingcoupler may be electrically directly connected between the sections ofthe system, as will be later set forth.

Another field of service for which my invention is adapted is inconnection with business conferences, where it is desired that any oneor all of a group of men present at the conference may take area-11s 18' ofllce telephone system. it is also applicable in a previouslyindicated as representing an independent telephone system, are omitted),including the Y microphone Mb and the speaker Sa of the amplifyingcoupler, constitute the instrumentalities by means of which any of theparties to theconference may communicate with the absent party. Themicrophone Mb is of a sufllcient sensitivity to receive messages fromany part of the room, while the speaker Si delivers incoming messages atsufiicient volume for all present to hear with ease.

Obviously, in an installation, such as just referred to, it is notnecessary that they coupling between the public telephone system and myamplifying coupler be of the acoustical type, but

the amplifying coupler may be electrically connected directly to thepublic telephone system, if desired, as will now be set forth withreference to Fig. 2 of the drawings.

In thisiigure, instead of employing an acousti cal coupling, as is shownin Fig. 1 between French telephone set F: and the microphone Ma andspeaker St, the telephone set F: is replaced in Fig. 2 with atransformer winding TW: of an auxiliary transformer Trawhile themicrophone M. is replaced by a transformer winding T'W. and.

the speaker Sh replaced with a transformer wlnding Two. The rest of thecircuit connections are the same as in Fig. 1, some of which are shownand identified by reference numerals. Thereotifying device RX- in Fig. 2is connected in shunt to the transformer winding 'I'W., and therectifying device RY is connected in shimt to the ti-3118'. formerwinding 34 of the auxiliary transformer 36. The operation of the system,partially shown in Fig. 2 and including direct electrical connectionsbetween the amplifying coupler and the telephone system A, will begenerally the same as that 7 already described, and no furtherdescription thereofisdeemednecessary.

Of course, when telephone systems A and B are interconnected, theamplifying coupler C may also be operativeiy associated with the twotelephone systems bymeans of direct electrical connections to both theinput side and output-side of the amplifying unit, in lieu of employingacoustical couplings, as illustrated in Fig. 1. In this case, theelectrical connections from telephone system A to the amplifier unit Ewill be as shown in Fig. 2, while the electrical connections totelephone system B will also be similarto those of Fig. 2, as will beunderstood.

In the foregoing description, microphones Ma and Mb have been set forthas connected in parallel relation, while the windings 28 and 34 of theauxiliary transformers 30 and 36, associated with the respectivespeakers S. and Sh, have been set forth as connected in series relation.However, the microphones and Mb are not necessarily connected in pa llelrelation. but may be arranged in series relation. For a betterunderstanding of these connections. I have shown this series relation ofthe microphones Ma and Ms in Fig. 3, to which reference is now made.

In this figure the microphone Ma, having one terminal connected byconductor It to ground, has its other terminal connected by conductorsl2 and I! to one terminal of microphone Mb, while the otherterminalthereof is connected by conductors I9 and 2| to the first amplifyingtube 2 of the amplifying unit E. Microphone Ma is provided with a shuntcircuit through the rectifying device RX by means of conductor 54, whilea shunt circuit is provided around microphone M by means of conductor 23which is connected to the upper terminal of the rectifying device Rx,while its lower terminal is connected by conductors 25 and I9 to theother terminal of the microphone Mb.

The general operation of the system with this series connection ofmicrophones is so similar to that already described, that no further description is deemed necessary.

Of course, if it is desired to connect the amplifying coupler byelectrical connections to the respective telephone systems A and B, asin Fig. 2,

the respective transformer windings TW- and its corresponding winding.We, (not shown but assumed'to be that of the transformer associated withthe telephone system B), may be connected in series relation, as will beunderstood from the foregoing description in connection with Figs. 2 and3, without further description.

While I now prefer to secure the desired control of the amplifier unitin the general manner hereinbefore indicated by means of rectifyingdevices operated in conjunction with an oscillator, with the rectifyingdevice connected in shunt circuit to the respective microphones M. andMn and 1 the transformer windings o'f'the speakers SI and ,Sb, in someinstances it may be founddesirable and expedient to utilize therectifying devices in series circuit with the foregoinginstrumentalities in such manner as to secure the same general operationof the amplifier imit.

In' Fig. 4 I have illustrated a system similar to that set forth in Fig.1, with the exception that the microphones Ma and Ms are connected inparallel relation, with the rectifying devices RX and am. respectivelyconnec in series therewith to ground, and the transformer windings ,2and I4 of the auxiliary transformers 3i and l are similarly connected inparallel but with the rectifying devices respectively connected inseries. therewith, instead of in shunt thereto. More specifically,thefirst amplif tube 2 understood.

of the electronic amplifying unit E is connected byconductors 8 and i8to one terminal of the microphone Mb, while its other terminal isconnected by conductor "to the upper terminal of the rectifying deviceRX having its lower terminal' connected through conductor 88 to ground.In parallel circuit therewithis the microphone Ma which is connectedfrom the first, amplifying tube 2 through conductors 8 and II to oneterminalthereof, while the other terminal is connected by conductor 90to the upper terminal of the rectifying device RX, having its lowerterminal connected by conductor 58 to ground.

On the output side of the amplifier unit E, power tube 4 is connectedthrough conductor 22, condenser 2i, conductor 28 to one terminal oftransformer winding 28, while the other terminal is connected byconductor 92 to the upper terminal of the rectifying device RY, havingits lower terminal connected through reactance 84, conductors 98 and 98,condenser ll and conductor 42 to the power tube 6.

In parallel relation therewith is the transformer winding 34 of theauxiliary transformer 36. The circuit for this transformer winding issystem, insofar as it is affected by the series connections of theseveral rectifying devices, will be outlined briefly.

Whenever rectifying device RX. in series circuit with the microphone M.is, by reason of the operation of the oscillator O, rendered active topass current to ground, the microphone Mn is operative and the amplifierunit E functions upon the electrical waves passing from telephone systemA to telephone system B. At this same time, by reason of its reverseconnection to the oscillator 0-, the rectifying device RXs is inactiveto pass current therethrough to ground, and hence microphone Mn isinoperative and the amplifying unit E is also inoperative upon theelectrical waves passing from telephone system B to telephone system A.

During the same time interval rectifying device RY, is inactive to passcurrent therethrough and hence the transformer 36 and its associatedspeaker Sb are inoperative. Similarly, during the same time interval therectifying device RY. becomes active to pass current and thereforeauxiliary transformer 30, together with its associated speaker Se, isrendered operative, as will be In this way by a somewhat diifere htmethod of control, the amplifying unit E is arranged to operatealternately on the electrical waves passing through the interconnectedsystem in oppo- 'site directions in the same general manner aspreviously described. I

' Of course, this series arrangement of the rectifying devices, whichhas been set forth in connection with Fig. 4, is equally applicable tosysing more or less specific details of constructiomz employed as anagency for permitting a two-wayconversation between a conference roomand a party to the public telephone system, as set forth' in connectionwith the foregoing description of Fig. 1.

While I have shown my invention as embodyadapted for two-waycommunication, comprising in combination, an electronic amplifier in-.

terconnecting both circuits of the respective sections, and means forcausingthe amplifier to operate alternately at a frequency aboveaudibility upon the electrical waves passing through the system inopposite directions.

2. An amplifying coupler for interconnecting two component sections ofan electrical system adapted for two-way communication; comprising incombination, an electronic amplifier interconnecting both circuits ofthe respective sections, and means for alternately interrupting theelectrical waves traversing the system in opposite directions at a highfrequency above audibility, and causing the interrupted waves inopposite directions to pass through the amplifier alternately in asuccession of intermittent pulsations of such rapid frequency that theinterruptions are inaudible to the listeners.

3. An amplifying coupler for interconnecting two component sections ofan electrical system' adapted for two-way communicatiomcomprising incombination, an electronic amplifier interconnecting both circuitsof therespective sections, and electrical means comprising a high frequencyoscillator and rectifying devicesfor interrupting the electrical wavespassing through the system in opposite directions in alternation and ata frequency above audibility to cause the amplifier to operatealternately first on the waves passing through the system in onedirection and then on the waves passing through the system in theopposite direction.

4. An amplifying coupler for interconnecting two component sections ofan electrical system adapted for two-way communication, comprising incombination, an electronic amplifier in-,

terconnecting both circuits of the respective sections, means includinga high frequency oscillater and rectifying devices in conjunctiontherewith and associated with both the incoming and outgoing circuitsofeach of said sections for simultaneously interrupting the electricalwaves passing in one. direction through the system at points bothaheadof and beyond the electronic amplifier and for simultaneouslyinterrupting the electrical waves passing through the system in theopposite direction at points both ahead of and beyond the electronicamplifier,'the respective simultaneous interruptions occurringalternately and at 180 time phase displacement the one with the otherand at a high frequency,

above audibility.

5. An amplifying coupler adapted to interconnect two component sectionsof an electrical system adapted for two-way communication,

comprising in combination, a single electronic amplifying unit adaptedto transmit and amplify amam .permanently connected in both circuits ofboth sections, a pair of rectifying devices of the Rector typerespectively connected in shunt to the two i'ncoming circuits, a pair ofsimilar rectifying devices respectively connected in shunt to the twooutgoing circuits, and a high frequency oscillator connected to theseveral rectifying devices to simultaneously cause the rectifying deviceassociated with one of said incoming circuits to become active-to passcurrent while the rectifying device associated with the other incomingcircuit is rendered inactive to pass current, and in 180 time phasedisplacement therewith, to simultaneously cause the rectifying deviceassociated with the outgoing circuit corresponding to the first namedincoming circuit to become active to pass current while the rectify!-ing device associated with the outgoing circuit corresponding tothesecond named incoming circuit is rendered inactive to pass current,

wherebythe electronic amplifier is operative at ing unit havingoperative connections to both circuits of the respective sections, andelectrical means operatively independent of the direction of fiow'of theelectrical waves for definitely controlling the operation of saidamplifying unit to cause it to alternately operate upon the electricalwaves passing through the interconnected sections in oppositedirections.

7. Anamplifying coupler foreinterconnecting two component sections of anelectrical system adapted for two-way communication, comprising incombination, a single electronic amplify- 7 ing unit having operativeconnections to both circuits of the respective sections, and means"including an extraneous source of alternating? current and rectifyingmeans associated there with for controlling the operation of theamplifying unit to render-it operative alternately upon the electricalwaves passing through the interconnected sections in one direction andthen upon the waves traversing the interconnected sections in theopposite direction.

8. An amplifying coupler forinterconnecting two component sections of anelectrical system adapted for two-way communication, comprising in'combination, a single electronic amplifying unit havingoperativejconnections to both circuits of the respective ,j sf'ections,the connections to the two incoming circuits to the amplifying unitbeing arranged in parallel and the connections to the two outgoingcircuits of the amplifying unit being arranged in series, recti:

fying devices severally arranged in shunt to each of the fourconnections, and electrical means as- 9. An'amplifying couplerforinterconnecting two separate and independent telephone systems both ofwhich are adapted for two-way communication, comprising incombination, asingle electronic amplifying unit, .means including acoustical couplingsfor connecting the receiving circuits of .both telephone systems to theinput side of said amplifying unit and the transmitting circuits of bothtelephone systems to the output side of said amplifying unit, andcontrol means operatively independent of the direction of flow of theelectrical waves and operating in a -definite 180 time phase relationfor simultaneously rendering inoperative the amplifier input connectionof one telephone system and the am li fler output connection of theother system and then simultaneously rendering inoperative the amplifierinput connection of the second system and the amplifier outputconnection of the first system, whereby the amplifying unit operatesalternately on the waves passing through the interconnected systems inopposite directions.

10. A system of two-way telephone communication, comprising incombination, two electrically independent telephone systems, such as apublic telephone system and a private interofiice telephone system, eachsystem being adapt! telephone system,'each system being adapted fortwo-way communication and each being provided with'the usual telephoneset comprising a receiver and a transmitter, an electronic amplifyingcoupler adapted to interconnect the respective telephone systems fortwo-way through communication, means'for acoustically coupling thereceiver and transmitter of each telephone system to said amplifyingcoupler, the receivers being connected to the input side of theamplifying coupler and the transmitters to the output side thereof, andcontrol means'associated with said coupler for causing the alternateamplifica tion of portions of the electrical waves passing through theinterconnected telephone systems in-opposite directions.

12.1An amplifying coupler for interconnecting two component sections ofan electrical system adapted for two-way communication, compris ing incombination. a single electronic amplilying unit having operativeconnections to both circuits of the respective sections, the connectionsto the two incoming and the two outgoing circuits to the amplifying unitbeing arranged "in series relation, rectifying devices severallyartelephone communiarcane simultaneously to pass current, whereby theamplifying unit operates alternately upon the waves traversing theinterconnected system in opposite directions.

13. A system of-two-way telephone communication, comprising incombination, a public telephone system adapted for two-waycommunication, a microphone, a speaker, an electronic amplifyingunitinterposed between and interconnecting the telephone system withsaid 1111610: phone and speaker, and electrical means operativelyindependent of the direction of flow of the electrical waves forcontrolling the operation of said amplifying unit to cause it toalternately operate upon electrical waves from the telephone system tosaid speaker and from said microphone to said telephone system inopposite directions.

14. An amplifying coupler adapted to interconnect two component sectionsof an electrical system adapted .for two-way communication, comprisingincombination', a single electronic amplifying unit adapted to transmitand amplify electrical waves of a two-way conversation and permanentlyconnected in both circuits of both sections, the two input circuits tothe amplifying unit being connected in parallel and the two outputcircuits from the amplifying unit being connected in parallel, a pair ofrectifying devices of the Rectox type respectively connected in seriest0 the two input circuits, a pair .of similar rectifying devicesrespectively connected in series to the two out-put circuits, and a highfrequency oscillator connected .to the several rectifying devices tosimultaneously cause the rectifying device associated with one of saidinput circuits to become active to pass current while the rectifyingdevice associated with the other input circuit is rendered inactive topass current, and in time phase displacement therewith, to

simultaneously cause the rectifying device associated with the outputcircuit corresponding to the first-named input circuit to become activeto pass current while the rectifying device associated with the outputcircuit corresponding to the second-named input circuit is renderedinactive to pass current, whereby the electronic amplifier is operativeat all times, but operates alternately .upon the electrical wavespassing in opposite directions through the system.

15. A method of operating an electronic amplifying couplerinterconnecting two component sections of a telephone system adapted fortwoway conversation which comprises modifying the operation of theamplifying coupler at a high frequency above audibility to cause it toalternately function on electrical waves passing through the system inopposite directions.

.16. A method of operating an electronic amplifying couplerinterconnecting two component sections of a telephone system adapted fortwoway conversation, which comprises passing electrical waves in-aseries of interrupted pulsations at a high frequency through theamplifying coupler and causing it to function alternately uponelectrical waves passing from one section to the other and then from thesecond-namedsection to the first-named section.

17. A method of repeating and amplifying a two-way telephoneconversation over two component sections of a telephone system, whichare interconnected by a single electronic ampliying unit, whichcomprises modifying the input and output connections of the amplifyingunit at a high frequency above audibility .to cause the amplifying unitto first repeatand amplify messages passing from-one section through theamplifying unit to the other section, while concurrently preventing itsoperation upon messages unit to the first section while preventing itsop-' eration upon messages passing in the first-named direction. a

18. A system. of two+way telephone communi-- cation comprising incombination two electrically independent telephone 'systems such as apublic telephone system and a private inter-ofllce telephone system,both of which are normally adapted for independent and conventionaltwo-way communication, and means electrically independent of bothtelephone systems and including a single electronic amplifying couplerand acoustical means for interconnecting said independent telephonesystems to cause them to function together as a single system fortwo-way telephone communication while maintaining the electricalindependence of said telephone systems.

19. A system of two-way telephone communication comprising incombination two electrically independent telephone systems as a publictelephone system and a private inter-ofllce telephone system, both'ofwhich are normally adapted for independent andmnventionaltwo-waycommunication, and means electrically independent of both ofsaid'systems for operatively coupling said systems together to causethem to function at amplified intensity as a single systein for two-waycommunication;

20. An amplifying coupler for interconnecting two electricallyindependent component sections of an electrical system of two-waycommunication, each of said component sections being adapted forcoinventional two-way communication and comprising a single electronicamplifying unit electrically separate and independent of both of saidcomponent sections, means for establishing an operative' acousticalconnection between each of said component sections and said amplifyingunit, whereby said amplifying unit is operatively interposed betweensaid component sections, and means for' controlling the operation ofsaid amplifying unit to cause it to alternately function on electricalwaves passing through the interconnected system in opposite directions.

.- THOMAS W, VARLEY.

